Aircraft: B767
Phase of flight: Parked
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence

Among the [maintenance issues] was [the] Standby Altimeter Vibrator. I spoke to the Dispatcher about another item; and then we talked about the Standby Altimeter. The operational notes were at best vague. '1. Weather at arrival and destination airport must be VMC. 2. Notify Dispatch.' Dispatcher assured me he had checked not only the departure and arrival airports; but our ETOPS; enroute; destination and [enroute] alternates as well. They were marginal; but were forecast to be VMC at the appropriate times.Approximately 45 minutes prior to push; we received an ACARS saying the ETOPS alternates were being changed because of a change in the forecast. They were no longer forecast to be VMC at the time of our arrival.We had uploaded the flight plan to the FMC; and checked all the points; but had not added the 'floating' waypoints for ETOPS entry; exit and ETP. Originally; we had EINN and CYYT as ETOPS alternates; but because of the deteriorating forecasts at these stations; had been changed to EGPK and CYQX. Given the time we had left; I requested a new briefing package as opposed to doing a pen and ink change.The new flight plan arrived some 10 minutes before push; and we hurriedly rechecked all the points to determine they were; as expected; all the same points and were still correct in the FMC. We did not add the floating waypoints as we were doing our best to push on time; and the fight plan showed 2:35 prior to ETOPS entry; I decided we could enter them after TOC. We were able to enter these within an hour of departure.As is my technique; I also put a 442 NM circle around Prestwick as another check on ETOPS entry. We had gotten our oceanic clearance; and just after our entry point into Class II showed on the ND; we also saw the circle I had put around EGPK crossing our course. This showed us entering ETOPS very near our entry point of LIMRI (W015). The flight plan had it much further west; at W02108.2. This made our entry approximately [an] hour sooner than the flight plan showed.Given the First Officer had never used SATCOM before; and with the clock ticking on our entry time; we made a SATCOM call to dispatch and asked why the entry point was the same as we had had when Shannon was our alternate. We were told that Shannon was still an adequate airport; so it did not need to be changed. A discussion followed that if EINN was still adequate (given the forecast WX conditions and DDG restrictions); the alternate would not have needed to be changed in the first place. I asked for new coordinates; and received new coordinates for ETOPS entry with Prestwick instead of Shannon. The dispatcher (not our original dispatcher) did not seem pleased by our request; but did give us some of what we requested. We also received our weather update at this time; which; if I recall was borderline as to being >30 minutes from entry at that point. We were never given the new lat/longs for ETP and exit points.Dispatch seemed annoyed at being questioned; and said we were legal to proceed. It is merely a dispatch requirement; not an operational one. I felt that I had a 'reasonable reliance' on the information dispatch had given me. B767-300ER Captain reported there was considerable confusion regarding proper dispatch procedures with the Standby Altimeter Vibrator inoperative.